JP2006201562A - Nonmagnetic one-component negative charge type spherical toner and color image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonmagnetic one-component negative charge type spherical toner providing stable color images free of degradation in image quality even in continuous printing and particularly suitable for use in a noncontact developing system while using large-particle-diameter alumina fine particles externally added as spacer particles, and also to provide a color image forming apparatus using the toner. <P>SOLUTION: The nonmagnetic one-component negative charge type spherical toner is obtained by externally adding alumina fine particles having an average particle diameter of 0.1-1.0 μm to toner base particles comprising at least a binder resin and a colorant and having a number average particle diameter of 4.5-9 μm, a particle size distribution in which an integrated value of ≤3 μm average particle diameter is ≤1%, and an average circularity of 0.95-0.99, wherein a work function (Φ<SB>t</SB>) of the toner base particles is made larger than a work function (Φ<SB>A</SB>) of the alumina fine particles at least by ≥0.4 eV. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a non-magnetic one-component negatively charged spherical toner and a color image forming apparatus in electrophotography.

  In electrophotography, an electrostatic latent image formed on a latent image carrier provided with a photoconductive substance is developed using a toner containing a colorant, and then transferred to an intermediate transfer medium, and further, paper or the like. The toner image is transferred to the recording material and fixed by heat, pressure or the like to form a copy or printed matter. In the case of using such a latent image carrier, for example, in Patent Document 1, alumina fine particles are used as external additive particles in toner base particles, and the latent image is supported by a polishing action on the surface of the latent image carrier. The body surface is always kept fresh, thereby preventing problems such as fogging and toner scattering and stable image formation, and alumina fine particles having a large particle size of 0.1 μm to 1.0 μm. Although it is described that the fine particles of the alumina particles are large, the adhesion force to the toner base particles is likely to be small due to the mass of the fine particles of the alumina particles having a small particle size, and it is easy to peel off. There is. In particular, the alumina fine particles have a high hardness, and there is a problem in that each member of the apparatus is polished if the amount of release from the toner base particles is large. In addition, if the amount of liberation is large, the powder characteristics and charging characteristics will be affected. Especially when continuous printing is performed, the behavior of the toner changes discontinuously, so that the obtained image quality such as image density and color reproducibility is uniform. This is a problem particularly in full-color images. In addition, if a toner having large particle size alumina fine particles as an external additive is applied to the non-contact development method, if the amount of large particle size alumina fine particles released from the toner base particles is large, the flying property is high. It has been found that various problems occur, such as a decrease in the stability of the printed image.

  Further, as a conventional technique related to external additives, for example, external addition of three types of external additives having different particle diameters to toner base particles is described in Patent Document 2 and JP-A No. 11-184144, Patent Document 3 and Japanese Patent Application Laid-Open No. 2003-322998 indicate that external additives or abrasives having a large particle size with a charging polarity opposite to that of the toner mother particles are externally added to the toner mother particles. Patent Document 4 discloses that fine particles are externally added. However, in any case, when continuous printing is performed for a long time, the external additive is released from the toner surface, and the free external additive is transferred to the latent image. There are problems such as adhesion to the surface of the carrier and the surface of the intermediate transfer medium, an increase in fog and reverse transfer toner, and a decrease in transfer efficiency. This phenomenon is caused by the release of the external additive having the opposite polarity or the negatively charged toner remaining after transfer, which is fixed on the latent image carrier and is not transferred to the intermediate transfer medium. There is a problem that the agent promotes wear on the surface of the developing member. For example, in the case of a non-magnetic one-component developing roller, the unevenness (Rz) on the surface thereof becomes small, causing a change in the amount of toner transported.

  Therefore, as a method for regulating the amount of free external additive, Patent Document 5, Japanese Patent Laid-Open No. 2002-189309, Japanese Patent Laid-Open No. 2002-207314, Japanese Patent Laid-Open No. 2002-236386, Japanese Patent Laid-Open No. 2002-258522, Japanese Patent Laid-Open No. 2003-207942, and Japanese Patent Laid-Open No. 2003-2003. -280240, JP-A-2003-280253, JP-A-2004-184719, and the like are known. Both improve cleaning, prevent wear of the latent image carrier, improve image quality and fluidity, and prevent filming and wear. As a result, there are still disadvantages in the stability of the printed image, various filming, the prevention of wear, and the improvement of the charging stability of the toner.

Further, for example, Patent Document 6, Japanese Patent Application Laid-Open No. 11-174726, Japanese Patent Application Laid-Open No. 2003-202696, and the like are known to define work functions of toner and external additives to improve image quality and stabilize charging characteristics. In addition, Patent Document 7 describes that the charging function and the transfer efficiency are improved by defining the work function of the external additive, but both of them can be used even after continuous printing of tens of thousands of pages. The initial toner characteristics cannot be maintained, and it is insufficient to prevent filming and wear and to provide a stable color image.
JP-A-8-69123 JP 63-289559 A JP 2002-318467 A JP 2003-322998 A JP 2001-117267 A JP-A-6-332236 JP 2003-295503 A

  The present invention can provide a stable color image without deterioration in image quality even in continuous printing, and is particularly suitable for application to a non-contact development system by externally adding alumina particles having a large particle size as spacer particles. An object is to provide a non-magnetic one-component negatively charged spherical toner and a color image forming apparatus using the toner.

The non-magnetic one-component negatively charged spherical toner of the present invention comprises at least a binder resin and a colorant, and has a number-based average particle diameter of 4.5 to 9 μm, and an integrated value of average particle diameters of 3 μm or less is 1. % Non-magnetic toner particles having an average particle size of 0.1 μm to 1.0 μm externally added to toner base particles having a particle size distribution of not more than% and an average circularity of 0.95 to 0.99. In the one-component negatively charged spherical toner, the work function (Φ _t ) of the toner base particles is at least 0.4 eV greater than the work function (Φ _A ) of the alumina fine particles.

The work function (Φ _t ) of the toner base particles is 5.2 to 5.8 eV, and the work function (Φ _A ) of the alumina fine particles is 4.8 to 5.3 eV.

  The alumina fine particles are α-type alumina fine particles.

  The toner base particles are obtained by a dissolution suspension method.

  The toner base particles are characterized in that the colorant contained in the toner base particles is present on the surface of the toner base particles.

  The non-magnetic one-component negatively charged spherical toner is a full color toner.

The color image forming apparatus of the present invention forms an electrostatic latent image on a latent image carrier, and sequentially develops the electrostatic latent image using a plurality of developing devices by a non-magnetic one-component method. In a color image forming apparatus in which a toner image formed on the latent image carrier is transferred to an intermediate transfer medium to form a color toner image, transferred onto a recording material, and fixed after the image is formed. Is composed of at least a binder resin and a colorant, and has a particle size distribution in which the average particle size based on the number is 4.5 to 9 μm, the integrated value of the average particle size of 3 μm or less is 1% or less, and A non-magnetic one-component negatively charged spherical toner obtained by externally adding alumina fine particles having an average particle size of 0.1 μm to 1.0 μm to toner base particles having an average circularity of 0.95 to 0.99, work function ([Phi _t) the work function of the alumina particles of the toner base particles ([Phi _a Characterized in that larger and more 0.4eV or more.

  The development system is a non-contact development system.

  The color image forming apparatus employs a four-cycle rotary development system.

  The color image forming apparatus employs a tandem developing system.

The non-magnetic one-component negatively charged spherical toner of the present invention can prevent the release of the alumina fine particles by making the work function (Φ _t ) of the toner base particles larger than the work function (Φ _A ) of the alumina fine particles having a large particle size. Color image quality can be output stably even for long-term continuous printing. In particular, when used for non-contact development, a non-magnetic one-component negatively charged spherical toner that does not cause a decrease in toner flying property can be obtained. Further, since the alumina fine particles having a large particle diameter are not liberated, the wear on the latent image carrier, the developing member, the regulating member, and the intermediate transfer medium can be reduced.

The toner with externally added large particle size alumina fine particles has the problem that large particle size alumina fine particles are liberated and stable color image quality cannot be achieved in long-term continuous printing, especially non-magnetic one-component non-contact development. When used in the system, the flying property of the toner is lowered, which is an obstacle to obtaining a stable color image quality, and it is necessary to reduce the liberation of large-diameter alumina fine particles. The inventors of the present invention make the work function (Φ _t ) of the toner base particles larger than the work function (Φ _A ) of the large-diameter alumina fine particles, that is, Φ _t > Φ _A , especially Φ _t −Φ _A > It has been found that a non-magnetic one-component negatively charged spherical toner with little release of alumina fine particles from toner base particles can be obtained in long-term continuous printing by setting the toner to 0.4 (eV).

  The nonmagnetic one-component negatively charged spherical toner in the present invention is formed by externally adding an external additive to toner base particles. The toner base particles can be produced by any of a pulverization method, a polymerization method, and a dissolution suspension method.

  As a method by the pulverization method, at least a pigment is contained in a binder resin, a release agent, a charge control agent and the like are added, mixed uniformly with a Henschel mixer, etc., melt-kneaded with a twin screw extruder, cooled, Through a pulverization-fine pulverization step, classification is performed to form toner base particles.

  Binder resins include polystyrene, poly-α-methylstyrene, chloropolystyrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-acetic acid. Vinyl copolymer, styrene-maleic acid copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-acrylic acid ester-methacrylic acid ester copolymer, styrene-α-chloroacrylic Homopolymer or copolymer containing styrene or styrene-substituted styrene resin such as acid methyl copolymer, styrene-acrylonitrile-acrylic acid ester copolymer, styrene-vinyl methyl ether copolymer, polyester resin, epoxy Resin, urethane modified epoxy Xylene resin, silicone modified epoxy resin, vinyl chloride resin, rosin modified maleic acid resin, phenyl resin, polyethylene, polypropylene, ionomer resin, polyurethane resin, silicone resin, ketone resin, ethylene-ethyl acrylate copolymer, xylene resin, polyvinyl butyral Resins, terpene resins, phenol resins, aliphatic or alicyclic hydrocarbon resins, etc. can be used alone or in combination.

  A colorant, a release agent, a charge control agent, and the like are added to the binder resin. Colorants for full color include carbon black, lamp black, magnetite, titanium black, chrome yellow, ultramarine, aniline blue, phthalocyanine blue, phthalocyanine green, Hansa Yellow G, rhodamine 6G, calco oil blue, quinacridone, benzidine yellow, rose bengal Malachite Green Lake, Quinoline Yellow, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 184, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 97, C.I. I. Pigment yellow 180, C.I. I. Solvent Yellow 162, C.I. I. Pigment blue 5: 1, C.I. I. Dye and pigment such as CI Pigment Blue 15: 3 can be used alone or in combination.

  Examples of the mold release agent include paraffin wax, microwax, microcrystalline wax, cadilla wax, carnauba wax, rice wax, montan wax, polyethylene wax, polypropylene wax, oxidized polyethylene wax, oxidized polypropylene wax and the like. Among these, it is preferable to use polyethylene wax, polypropylene wax, carnauba wax, ester wax and the like.

  As the charge control agent, oil black, oil black BY, Bontron S-22 (manufactured by Orient Chemical Industry Co., Ltd.), Bontron S-34 (manufactured by Orient Chemical Industry Co., Ltd.), salicylic acid metal complex E-81 (Orient Chemical) Industrial Co., Ltd.), thioindigo pigments, sulfonylamine derivatives of copper phthalocyanine, Spiron Black TRH (manufactured by Hodogaya Chemical Co., Ltd.), calixarene compounds, organic boron compounds, fluorine-containing quaternary ammonium salt compounds, Examples include monoazo metal complexes, aromatic hydroxyl carboxylic acid metal complexes, aromatic dicarboxylic acid metal complexes, polysaccharides, and the like. Of these, colorless or white toners are preferred for color toners.

  The component ratio in the toner base particles is 0.5 to 15 parts by weight, preferably 1 to 10 parts by weight, and 1 to 10 parts by weight of the release agent with respect to 100 parts by weight of the binder resin. The charge control agent is 0.1 to 7 parts by mass, preferably 0.5 to 5 parts by mass.

  The pulverized toner is preferably spheroidized in order to improve transfer efficiency. In the pulverization process, a relatively round spherical device capable of being pulverized, for example, a turbo mill known as a mechanical pulverizer (manufactured by Turbo Kogyo Co., Ltd.). ) Can be used to increase the degree of circularity to 0.93, and the degree of circularity can be increased to 1.00 by using a hot air spheronizing device (manufactured by Nippon Pneumatic Industry) for the pulverized toner. .

  As the toner base particles in the present invention, the average circularity is adjusted to 0.95 to 0.99, including toner base particles obtained by a polymerization method described later and toner base particles obtained by a dissolution suspension method. If the circularity is less than 0.95, a desired transfer efficiency cannot be obtained, and if it is more than 0.99, there is a problem in cleaning properties.

  Next, the polymerization toner is obtained by a suspension polymerization method, an emulsion polymerization method, a dispersion polymerization method, or the like, and can be made suitable for a full color toner. In the suspension polymerization method, a polymerizable monomer, a color pigment, a release agent, and a complex added with a dye, a polymerization initiator, a crosslinking agent, a charge control agent, and other additives as necessary are dissolved or dissolved. The dispersed monomer composition is added to an aqueous phase containing a suspension stabilizer (water-soluble polymer, poorly water-soluble inorganic substance) with stirring, granulated, and polymerized to obtain a desired particle size. The colored polymer toner particles are formed. In the materials used for the production of the polymerization toner, the same materials as those of the pulverized toner described above can be used for the colorant, release agent, and charge control agent. In the emulsion polymerization method, polymerization is performed by dispersing a monomer and a mold release agent, and if necessary, a polymerization initiator and an emulsifier (surfactant) in water, and then aggregating with a colorant, a charge control agent, and the like. Colored toner particles having a desired particle size are formed by adding an agent (electrolyte) or the like.

  Examples of the polymerizable monomer component include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-ethylstyrene, vinyltoluene, 2,4-dimethyl. Styrene, pn-butylstyrene, p-phenylstyrene, p-chlorostyrene, divinylbenzene, methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, n-octyl acrylate, Dodecyl acrylate, hydroxyethyl acrylate, 2-ethylhexyl acrylate, phenyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate , N-octyl methacrylate, dodecyl methacrylate, hydroxyethyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, acrylic acid, methacrylic acid, maleic acid, fumaric acid, cinnamic acid, ethylene glycol, Propylene glycol, maleic anhydride, phthalic anhydride, ethylene, propylene, butylene, isobutylene, vinyl chloride, vinylidene chloride, vinyl bromide, vinyl fluoride, vinyl acetate, vinyl propyleneate, acrylonitrile, methacrylonitrile, vinyl methyl ether, vinyl Examples include ethyl ether, vinyl ketone, vinyl hexyl ketone, and vinyl naphthalene. Examples of the fluorine-containing monomer include 2,2,2-trifluoroethyl acrylate, 2,2,3,3-tetrafluoropropyl acrylate, vinylidene fluoride, ethylene trifluoride, tetrafluoroethylene, trifluoropropylene, and the like. Can be used as a binder resin in negatively charged toner because fluorine atoms are effective for negative charge control.

  Examples of the emulsifier (surfactant) include sodium dodecylbenzene sulfate, sodium tetradecyl sulfate, sodium pentadecyl sulfate, sodium octyl sulfate, sodium oleate, sodium laurate, potassium stearate, calcium oleate, dodecyl ammonium chloride, dodecyl ammonium bromide. , Dodecyl trimethyl ammonium bromide, dodecyl pyridinium chloride, hexadecyl trimethyl ammonium bromide, dodecyl polyoxyethylene ether, hexadecyl polyoxyethylene ether, lauryl polyoxyethylene ether, sorbitan monooleate polyoxyethylene ether, and the like.

  Examples of the polymerization initiator include potassium persulfate, sodium persulfate, ammonium persulfate, hydrogen peroxide, 4,4′-azobiscyanovaleric acid, t-butyl hydroperoxide, benzoyl peroxide, 2,2′-azobis- There are isobutyronitrile and the like.

  Examples of the flocculant (electrolyte) include sodium chloride, potassium chloride, lithium chloride, magnesium chloride, calcium chloride, sodium sulfate, potassium sulfate, lithium sulfate, magnesium sulfate, calcium sulfate, zinc sulfate, aluminum sulfate, and iron sulfate. Can be mentioned.

  As a method for adjusting the circularity of the polymerization toner, the emulsion polymerization method can freely change the circularity by controlling the temperature and time during the aggregation process of the secondary particles, and its range is from 0.94 to 1. In the suspension polymerization method, since a true spherical toner is possible, the circularity can be in the range of 0.98 to 1.00. In order to set the average circularity to 0.95 to 0.99, it can be adjusted as appropriate by heat-deforming at or above the Tg temperature of the toner.

  Next, the dissolution suspension method toner will be described. As the binder resin, the binder resin described in the above section of the pulverized toner can be used, but a polyester resin is preferable from the viewpoint of color developing properties. Examples of the polyester resin include those described in JP-A No. 2003-140380, which is a dehydration condensate of a polybasic carboxylic acid and a diol, a cross-linked polyester resin having a high molecular weight and high viscosity, and a low molecular weight A blend of a branched or linear polyester resin with low viscosity is preferable. Moreover, it is good to have acidic groups, such as a carboxyl group, a sulfone group, and a phosphoric acid group, and among them, a carboxyl group-containing polyester resin is preferable. A polyester resin having an acid value of 3 to 20 mg KOH / g is preferable, and the reaction rate with bifunctional carboxylic acids and diols is adjusted, or trimellitic anhydride is used as a polybasic acid component. A carboxyl group-containing polyester resin is preferable because it is excellent in dispersion stability and can be negatively charged when formed into toner base particles.

  The solution suspension method toner base particles may be prepared by the method described in JP-A-2003-140380 using the binder resin thus obtained, and the colorant described in the section of binder resin and pulverized toner, If necessary, a release agent and a charge control agent are dissolved and dispersed in an organic solvent, and then an aqueous medium is gradually added to the resulting organic solvent to be dissolved and dispersed, followed by phase inversion emulsification. Can be formed. The obtained fine particles are agglomerated and granulated into colorant-containing resin fine particles having a desired size, and can be converted into toner mother particles through separation, washing and drying steps. In the dissolution suspension method, toner mother particles can be produced while controlling emulsification and association.

  In the step of dissolving / dispersing in an organic solvent, after dissolving the binder resin in the organic solvent, a preliminarily dispersed colorant may be additionally added to prepare a solution / dispersion in the organic solvent. In the phase inversion emulsification step, ion-exchanged water (aqueous medium) containing a basic neutralizing agent is gradually added to the solution / dispersion to form a suspension / emulsion. Water may be added so that the ratio of water to the total amount of added water is 35 to 65% by mass.

  Examples of the basic neutralizing agent used for phase inversion emulsification include inorganic bases such as sodium hydroxide, potassium hydroxide, ammonia, diethylamine, and triethylamine, and organic bases. Organic solvents include hydrocarbons, halogenated hydrocarbons, ethers, ketones, and esters. Specifically, hexane, heptane, toluene, xylene, cyclohexane, methylcyclohexane, methyl chloride, dichloromethane, and ethyl chloride. Propyl chloride, dioxane, tetrahydrofuran, acetone, methyl ethyl ketone, ethyl acetate, propyl acetate and the like, or a mixture of two or more thereof. In addition, as a mixer used in the emulsification step, an emulsifying disperser such as a homomixer, a slasher, a homogenizer, a colloid mill, a media mill, and a cavitron can be used.

  The number average particle size of the toner base particles and toner particles described later in the present invention is preferably 9 μm or less for all of the pulverized toner base particles, the polymerization method toner base particles, and the dissolution suspension method toner base particles. More preferably, it is 5 μm. For toner particles having a number average particle size larger than 9 μm, even when a latent image is formed at a high resolution of 1200 dpi or higher, the reproducibility of the resolution is lower than that of a small particle size toner, and is 4.5 μm or less. As a result, the concealability by the toner decreases, and the amount of the external additive used to increase the fluidity increases, and as a result, the fixing performance tends to decrease.

  In the particle size distribution based on the number of toner base particles, the integrated value of particles having an average particle size of 3 μm or less is 1% or less, preferably 0.8% or less. When the average value of the average particle size of 3 μm or less exceeds 1%, charging by the toner layer regulating member becomes insufficient, which causes undesirable generation of reversely charged toner and filming on the latent image carrier. .

  The number average particle diameter, particle size distribution, and average circularity of the above-described toner base particles and toner particles described later in the present invention are values measured by a flow type particle image analyzer (FPIA2100 manufactured by Sysmex).

As the toner base particle shape, toner particles having a shape close to a true sphere are preferable. Specifically, the toner base particles are represented by the following formula:
R = L ₀ / L ₁
{However, in the formula, L ₁ (μm) is the perimeter of the projected image of the toner particles to be measured, and L ₀ (μm) is a perfect circle having an area equal to the area of the projected image of the toner particles to be measured (completely The perimeter of a geometric circle). }
The average circularity (R) represented by the formula is 0.95 to 0.99, preferably 0.972 to 0.983. As a result, the transfer efficiency is high, and even when continuous printing is performed, there is little fluctuation in the transfer efficiency, the charge amount is stabilized, and the toner has excellent cleaning properties.

  Next, the work function (Φ) is known as the energy required to extract electrons from the substance. The smaller the work function, the easier it is to emit electrons, and the larger the work function, the less difficult it is to emit electrons. Therefore, external addition of alumina fine particles having a work function smaller than the work function of the toner base particles to the negatively chargeable toner base particles can make the toner base particles more negatively charged, and also improves adhesion to the alumina fine particles. It will be excellent.

  The work function is measured by the following measurement method, is quantified as energy (eV) for extracting electrons from the material, and can evaluate the chargeability by contact between various materials. The work function is measured using a surface analyzer (AC-2, low energy electronic counting method manufactured by Riken Keiki Co., Ltd.). In the present invention, the apparatus uses a deuterium lamp, the developing roller subjected to metal plating has an irradiation light amount of 10 nW, and in other measurements, the irradiation light amount is set to 500 nW, and monochromatic light is selected by a spectrometer. The sample is irradiated with a spot size of 4 mm square, an energy scanning range of 3.4 to 6.2 eV, and a measurement time of 10 sec / 1 point. The photoelectrons emitted from the sample surface can be detected and processed using work function meter software. The work function is measured with a repeatability (standard deviation) of 0.02 eV. . Note that, as a measurement environment for ensuring data reproducibility, a 24-hour left-over product is used as a measurement sample under the conditions of operating temperature and humidity of 25 ° C. and 55% RH.

  As shown in FIGS. 1 (a) and 1 (b), the toner dedicated measurement cell has a shape having a toner containing recess having a diameter of 10mm and a depth of 1mm at the center of a stainless steel disk having a diameter of 13mm and a height of 5mm. The sample toner is put into the concave portion of the cell without being tamped using a weighing sledge, and then subjected to measurement in a state where the surface is leveled and flattened using a knife edge. After the measurement cell filled with toner is fixed on the specified position of the sample stage, the irradiation light quantity is set to 500 nW, the spot size is set to 4 mm square, and the measurement is performed under the conditions of the energy scanning range of 4.2 to 6.2 eV.

  In addition, in the case where an image forming apparatus member having a cylindrical shape such as a photoconductor or a developing roller, which will be described later, is used as a sample, the cylindrical image forming apparatus member is cut to a width of 1 to 1.5 cm, and then a ridge line 2A to obtain a measurement specimen having the shape shown in FIG. 2A, and then the measurement light is irradiated onto the specified position of the sample stage as shown in FIG. 2B. The irradiation surface is fixed so as to be smooth with respect to the direction. Thereby, the emitted photoelectrons are efficiently detected by the detector (photoelectron tube). When the intermediate transfer belt, the regulating blade, and the photosensitive member are in the form of a sheet, the measurement light is irradiated with a 4 mm square spot as described above, so that the sample piece is cut out to a size of at least 1 cm square. Similar to 2 (b), it is fixed on the sample stage and measured in the same manner.

  In this surface analysis, when the excitation energy of monochromatic light is scanned from low to high, photon emission starts from a certain energy value (eV), and this energy value is called a work function (eV). FIG. 3 shows an example of a chart obtained for the toner. FIG. 3 shows the excitation energy (eV) as the horizontal axis and the normalized photon yield (photon yield per unit photon as the nth power) as the vertical axis, and a constant slope (Y / eV) is obtained. . In the case of FIG. 3, the work function is indicated by the excitation energy value (eV) at the inflection point (A).

The following are examples of the production of toner base particles in the invention by the dissolution suspension method and their physical properties.
(Production Example 1 of toner mother particles)
・ Polycondensed polyester resin {manufactured by Sanyo Chemical Industries, Hymer ES-801, mass ratio of non-crosslinked component to crosslinked component (45/55)} 110 parts by mass Carnauba wax 55 parts by mass Cyan pigment (phthalocyanine α type) 55 parts by mass was melt-kneaded with a pressure kneader. After cooling the melt-kneaded product, it is roughly crushed to a size of 1 to 2 mm square, and using a colloid mill manufactured by Nippon Seiki Seisakusho, 210 parts by mass of the melt-kneaded product, 80 parts by mass of the polycondensation polyester resin, 245 parts by mass of methyl ethyl ketone was mixed and stirred.

  Next, 1N ammonia water was added and sufficiently stirred, and then 160 parts by mass of ion-exchanged water was added and further stirred at 30 ° C. for 1 hour. And 150 mass parts ion-exchange water was dripped, and the fine particle dispersion was prepared by phase inversion emulsification. Next, after adding 400 parts by mass of ion-exchanged water, the mixture was heated to a temperature equal to or higher than the boiling point of methyl ethyl ketone to remove the solvent, and finally the solid content was adjusted to about 34%.

  Then, 235 parts by mass of the obtained fine particle dispersion was diluted with ion-exchanged water, the solid content was adjusted to about 20%, 60 parts by mass of 20% saline was added, and the temperature was raised to 68 ° C. The mixture was stirred for 60 minutes, and then 0.6 part by weight of nonionic emulsifier NL-250 (Daiichi Kogyo Seiyaku Co., Ltd.) was added and stirred at 70 ° C. for 4 hours to complete granulation.

  The obtained slurry is separated with a centrifuge, washed, and then the water content in the toner base particles is 0.5% or less by mass ratio using a vibrating fluidized bed apparatus manufactured by Chuo Kakoh Co., Ltd. Then, cyan toner base particles were obtained.

  The average particle diameter and average circularity on the basis of the number of the cyan toner base particles obtained measured by “Flow type particle image analyzer FPIA-2100” manufactured by Sysmex Corporation are shown in Table 2 below, and “ Table 1 below similarly shows the results of measuring the work function using the photoelectron spectrometer AC-2 "with a measurement light amount of 500 nW. The integrated value of the average particle diameter of 3 μm or less was 0.34%.

(Toner base particle production example 2)
Magenta toner base particles were produced in the same manner as in Production Example 1 of toner base particles, except that the colorant was changed to Carmine 6B.
The average particle diameter, average circularity, and work function based on the number of magenta toner base particles obtained are similarly shown in Table 1 below. The integrated value of the average particle diameter of 3 μm or less was 0.76%.

(Toner mother particle production example 3)
In Production Example 1 of toner base particles, the colorant was changed to P.I. Y. Yellow toner mother particles were produced in the same manner except that the amount of the toner was changed to 155.
The average particle diameter, average circularity, and work function based on the number of yellow toner base particles obtained are similarly shown in Table 1 below. The integrated value of the average particle diameter of 3 μm or less was 0.31%.

(Toner base particle production example 4)
Black toner base particles were produced in the same manner as in Production Example 1 of toner base particles, except that the colorant was replaced with surface-treated carbon black 1 (carbon M1000 manufactured by Mitsubishi Chemical Corporation). The average particle diameter, average circularity, and work function based on the number of black toner base particles obtained are similarly shown in Table 1 below. The integrated value of the average particle diameter of 3 μm or less was 0.31%.

(Toner mother particle production example 5)
In the toner mother particle production example 1, instead of the polycondensation polyester resin, a polycondensation polyester resin of an aromatic dicarboxylic acid and an alkylene etherified bisphenol A, and a partially crosslinked product of the polycondensation polyester resin with a polyvalent metal compound Cyan toner base particles were prepared in the same manner except that a 50:50 (mass ratio) mixture (manufactured by Sanyo Chemical Industries Co., Ltd.) was used and the colorant was changed to phthalocyanine β type which is a cyan pigment.
The average particle diameter, average circularity, and work function based on the number of cyan toner base particles obtained are similarly shown in Table 1 below. The integrated value of the average particle diameter of 3 μm or less was 0.33%.

(Production Example 6 of toner mother particles)
Magenta toner mother particles were produced in the same manner as in toner mother particle production example 5 except that the colorant was replaced with dimethylquinacridone.
The average particle diameter, average circularity, and work function based on the number of magenta toner base particles obtained are similarly shown in Table 1 below. The integrated value of the average particle diameter of 3 μm or less was 0.42%.

(Toner mother particle production example 7)
In Production Example 5 of toner base particles, the colorant is P.I. Y. Yellow toner mother particles were produced in the same manner except that the particle size was changed to 93.
The average particle diameter, average circularity, and work function based on the number of yellow toner base particles obtained are similarly shown in Table 1 below. The integrated value of the average particle diameter of 3 μm or less was 0.32%.

(Production Example 8 of Toner Base Particles)
Black toner base particles were produced in the same manner as in Production Example 5 of toner base particles, except that the colorant was replaced with surface-treated carbon black 2 (carbon M1000 manufactured by Mitsubishi Chemical Corporation). The average particle diameter, average circularity, and work function based on the number of black toner base particles obtained are similarly shown in Table 1 below. The integrated value of the average particle diameter of 3 μm or less was 0.31%.

  Table 2 shows the work function value of each colorant.

  As is clear from Tables 1 and 2, the work function of the dissolution suspension method toner base particles is greatly influenced by the type of the colorant, although it varies depending on the components such as the resin and the charge control agent. . This indicates that the colorant is distributed or exposed near the surface of the toner base particles.

Next, the external additive will be described.
The non-magnetic one-component negatively charged spherical toner of the present invention is a toner obtained by externally adding large particles of alumina particles having an average particle size of 0.1 μm to 1.0 μm to toner base particles. By externally adding, it is possible to improve the durability of the toner and to improve the developability during non-contact development as spacer particles. The alumina fine particles are industrially obtained by the so-called Bayer method, in which aluminum hydroxide obtained by treating bauxite raw material with sodium hydroxide is calcined in the atmosphere to form α-type alumina. However, since a large amount of sodium remains and inhibits electrical insulation, JP-A-8-290914, for example, describes α-type alumina fine particles having a high purity and a narrow particle size distribution with a sodium content of 100 ppm or less. Japanese Patent Laid-Open No. 2003-26419 describes a method for producing α-type alumina fine particles by acid treatment, and Japanese Patent Laid-Open No. 7-41318 discloses a fluoride mineralizer and α-type alumina as a raw material alumina source. A desired α-type alumina having a desired average particle size and a primary particle size distribution can be obtained by adding seed crystals of particles and firing at 1500 ° C. or lower. As described, various alumina fine particles have been developed.

(Outline of production example of α-type alumina fine particles 1 and 2)
This is a method described in JP-A-8-290914, and pulverizes transition alumina obtained by calcining aluminum hydroxide produced by the Bayer method so that the average particle diameter is 0.1 to 0.3 nm. Next, α-type alumina fine particles are obtained by firing at 1150 to 1300 degrees in an atmosphere gas containing 1% by volume or more of hydrogen chloride gas and 0.1% by volume or more of water vapor. “AKP-53” manufactured by Sumitomo Chemical Co., Ltd. was used as the α-type alumina 1 produced by this method, and “AKP-50” manufactured by Sumitomo Chemical Co., Ltd. was used as the α-type alumina 2.

(Outline of production example of alumina fine particles 3 and 5)
This is a method described in JP-A-7-41318. Aluminum hydroxide produced by the Bayer method and transition alumina pulverized to an average particle size of 0.2 to 0.5 nm are used as raw material alumina, and are converted into alumina. Adding 0.02 to 0.3% by mass of fluoride mineralizer and 5% by mass of α-type alumina fine particles having an average particle size of 1 μm or less with respect to the raw material alumina, and firing at 1350 ° C. Thus, α-type alumina fine particles can be obtained. “LS-235” manufactured by Nippon Light Metal Co., Ltd. was used as the α-type alumina 3 produced by this method, and “LS-250” manufactured by Nippon Light Metal Co., Ltd. was used as the α-type alumina 5.

(Outline of production example of α-type alumina fine particles 4)
This method is described in JP-A-2003-26419. After adding 10% by mass of DL-lactic acid to an aqueous solution containing 23% by mass of basic aluminum chloride in terms of aluminum oxide, 2 kg / cm ² , 120 ° C., 20 Hydrothermal treatment for a period of time, heating and drying at 60 ° C. to gel so that the average particle size becomes 0.1 to 0.3 nm, and the resulting composite gel is heated at about 600 ° C. in the atmosphere. As a result, α-type alumina fine particles are obtained. As the α-type alumina 4 produced by this method, “TM-D” manufactured by Daimei Chemical Co., Ltd. was used.

  Table 3 shows physical properties of each alumina fine particle. The particle size of the external additive in the present invention is obtained by actually measuring the particle size of 500 arbitrary particles of an electron microscope image of 100,000 times, and is a number average particle size.

The present inventor examined the suitability of the various alumina fine particles as described above as external additives to the toner base particles, and the work function (Φ _A ) was in the range of 4.9 to 5.3 depending on the production method. It showed various values and was not uniform. In the nonmagnetic one-component negatively charged spherical toner of the present invention, as will be described later, by making the work function (Φ _t ) of the toner base particles at least 0.4 eV or more than the work function (Φ _A ) of the alumina fine particles, The negatively charged toner base particles can be made more negatively charged and the adhesion to the externally added alumina fine particles can be enhanced. The difference in work function between the toner base particles and the alumina fine particles described above is at least 0. It is preferable to select α-type alumina fine particles that are 4 eV or more. For example, in the above-described toner mother particle production example 1, the work function is 5.34 eV. In this case, α-type alumina 1 is preferable as the α-type alumina fine particles.

  The addition amount of the alumina fine particles having a large particle size with respect to the toner base particles is 0.05 to 1.3 parts by weight, preferably 0.1 to 1.0 parts by weight with respect to 100 parts by weight of the toner base particles. . When the amount is less than 0.05 parts by mass, the function as a spacer is not achieved, and when the amount is more than 1.3 parts by mass, the amount of released alumina particles having a large particle size increases, which is not preferable.

  The external additive added in addition to the alumina fine particles will be described. First, hydrophobically charged negatively charged silica fine particles are exemplified.

  As the negatively chargeable silica fine particles, those having an average particle diameter of 4 to 120 nm, preferably 5 to 70 nm, and more preferably 6 to 60 nm are used. The smaller the average particle diameter of the negatively chargeable silica fine particles, the higher the fluidity of the obtained toner. Moreover, when it exceeds 120 nm, there exists a possibility that fluidity | liquidity may worsen extremely.

  As the negatively chargeable silica fine particles, negatively chargeable silica fine particles having a uniform particle diameter may be used alone, but it is preferable to use two or more negatively chargeable silica fine particles having different average particle diameters in combination. Generally, negatively-charged silica fine particles (small particle size silica) having a small average particle size are used, and this is used in combination with negatively-charged silica fine particles (large particle size silica) having a large average particle size. As a result, the absolute value of the charge amount can be increased as compared with the case of using only a small particle size silica, and the large particle size silica becomes resistance, and the small particle size silica is embedded in the toner base particles. Therefore, long-term charging stability is improved. Furthermore, it is possible to improve the fluidity of the toner, exhibit a blocking effect against heat, and improve the storage stability of the toner. Preferably, negatively charged silica fine particles having an average particle size of 5 to 20 nm, preferably 6 to 15 nm as small particle size silica, and negative particles having an average particle size of 20 to 70 nm, preferably 20 to 60 nm, as large particle size silica. It is preferable to use in combination with the chargeable silica fine particles. The difference in average particle size between the large particle size silica and the small particle size silica is preferably 10 nm or more, and more preferably 20 nm or more.

  The addition ratio of large particle size silica to small particle size silica is 1: 3 to 3: 1, preferably 1: 2 to 2: 1, more preferably 1: 1.5 to 1.5: by weight. A value of 1 is preferable for imparting fluidity to the toner and obtaining long-term charging stability. When using large particle size silica and small particle size silica, they may be mixed and added to the toner base particles at the same time, either one may be added first, and then the other may be added.

  The addition amount of the negatively chargeable silica fine particles can vary depending on the particle size distribution or fluidity of the toner base particles, or the particle size distribution of the external additive, the desired charge amount, and the like. For example, in the case of silica having the small particle diameter, 0.5 to 2.0 parts by mass, preferably 0.7 to 1.5 parts by mass are added to 100 parts by mass of the toner base particles. In the case of a large particle size silica, 0.2 to 2.0 parts by mass, preferably 0.3 to 1.5 parts by mass is added. When the large particle size silica and the small particle size silica are used in combination, the total amount is 0.5 to 3.0 parts by mass, preferably 0.7 with respect to 100 parts by mass of the toner base particles, taking the above mixing ratio into consideration. Add ~ 2.5 parts by weight.

  The negatively chargeable silica fine particles are preferably hydrophobized. By making the surface of the negatively chargeable silica fine particles hydrophobic, the fluidity and chargeability of the toner are further improved. Hydrophobization of silica fine particles can be achieved by using silane compounds such as aminosilane, hexamethyldisilazane and dimethyldichlorosilane; or dimethyl silicone, methylphenyl silicone, fluorine-modified silicone oil, alkyl-modified silicone oil, amino-modified silicone oil, epoxy-modified silicone oil, etc. This silicone oil is used, for example, by a method commonly used by those skilled in the art, such as a wet method or a dry method. Examples of the hydrophobic negatively chargeable silica fine particles include commercially available RX200 and RX50 manufactured by Nippon Aerosil Co., Ltd., TG811F, TG810G, and TG308F manufactured by Cabot Corporation.

  The work function of the hydrophobic silica particles is in the range of 5.0 to 5.3, but is preferably at least 0.05 ev or less than the toner base particles. Thereby, the hydrophobic silica particles can be fixed to the toner base particles by the charge transfer due to the work function difference.

  Further, as external additive particles in the present invention, fine particles of titanium oxide having a relatively low electrical resistivity are added in addition to silica fine particles subjected to hydrophobic treatment. Titanium oxide can take crystal forms such as rutile, anatase, and rutile-anatase. Any crystalline titanium oxide may be used, but the rutile-anatase type titanium oxide is easy to adjust the charge, and even if the number of printed sheets increases, the titanium oxide particles are not easily embedded in the toner base particles. It is preferably used in terms of Although there is no restriction | limiting in particular in the magnitude | size of a titanium oxide microparticles | fine-particles, it is preferable that a particle size or a length of a major axis is a magnitude | size of 10-200 nm. In the case of rutile-anatase-type titanium oxide, titanium oxide fine particles having a major axis of about 10 to 200 nm are preferable.

  The titanium oxide fine particles are added in an amount of 0.2 to 2.0 parts by weight, preferably 0.3 to 1.5 parts by weight, based on 100 parts by weight of the toner base particles. When titanium oxide fine particles and positively chargeable silica fine particles are used, the charge is added in a mass ratio of 1: 3 to 3: 1 without causing an extreme decrease in the electric resistance of the toner. It is preferable at the point which can adjust.

  The surface of the fine particles of titanium oxide is hydrophobic in order to reduce the change in chargeability with respect to changes in the external environment of the toner (that is, maintain stable chargeability) and improve the fluidity of the toner. Is preferable. Hydrophobization of the titanium oxide fine particles is carried out by the same method as that of the negatively chargeable silica fine particles. Examples of the hydrophobic titanium oxide fine particles include STT-30S manufactured by Titanium Industry Co., Ltd.

  The work function of the hydrophobic titanium oxide particles is in the range of 5.5 to 5.7 eV, and may be externally added to the toner base particles together with the hydrophobic silica particles having a small particle diameter. If the work function of the titanium oxide particles is substantially the same (the absolute value difference is within 0.1 eV), the toner base particles are first externally treated with hydrophobic silica particles, and then the metal soap described later is used. It is preferable to externally add together with the particles.

  When the work function is substantially the same as that of the toner base particles, it is difficult to adhere directly to the toner base particles. However, since the work function can be attached to the toner base particles through the surface of the hydrophobic silica particles having a small work function, it is excessive. Charge transfer from the charged hydrophobic silica particles can be facilitated, and overcharging in the hydrophobic silica particles can be more effectively prevented, which is preferable.

Inorganic fine particles other than titanium oxide fine particles can also be externally added for the purpose of controlling the chargeability and improving the fluidity. For example, as inorganic fine particles, metal oxide fine particles such as strontium oxide, tin oxide, zirconia oxide, magnesium oxide, and indium oxide, nitride fine particles such as silicon nitride, carbide fine particles such as silicon carbide, calcium sulfate, barium sulfate, Examples thereof include fine particles of metal salts such as calcium carbonate, and inorganic fine particles such as a composite thereof. Metal oxide fine particles having an electrical resistivity of 10 ⁹ Ωcm or less and a relatively small electrical resistivity are preferably used. Although there is no restriction | limiting in particular in the magnitude | size of the inorganic fine particle to add, It is preferable that a particle size is a magnitude | size of 10-300 nm. These inorganic fine particles are preferably subjected to a hydrophobic treatment on the surface for the purpose of stabilizing charging characteristics. For the hydrophobization treatment, the same method as any of the above-described hydrophobic methods for the negatively chargeable silica fine particles and the positively chargeable silica fine particles is employed.

  In the toner production method of the present invention, after the toner base particles and the inorganic external additive particles described above are mixed, positively charged silica fine particles and long chain fatty acids are used as the processed product and external additive particles. Alternatively, it may be mixed with the salt.

  The positively charged silica fine particles are preferably subjected to a hydrophobic treatment. By making the surface of the positively chargeable silica fine particles hydrophobic, the change in the chargeability with respect to the change in the external environment of the toner is reduced (that is, the stable chargeability is maintained) and the fluidity of the toner is improved. Therefore, it is preferable. The hydrophobization of the positively chargeable silica fine particles is performed by the same method as the above-described hydrophobization of the negatively chargeable silica fine particles. Examples of the hydrophobic positively chargeable silica fine particles include commercially available NA50H manufactured by Nippon Aerosil Co., Ltd. and TG820F manufactured by Cabot Co., Ltd.

  The positively chargeable silica fine particles have a volume average particle diameter of 10 to 50 nm, preferably 15 to 40 nm in consideration of fluidity. The positively chargeable silica fine particles are added in an amount of 0.1 to 1.0 parts by weight, preferably 0.2 to 0.8 parts by weight, based on 100 parts by weight of the toner base particles. When the negatively chargeable resin is used as the binder resin and the negatively chargeable silica fine particles are not used as the charge control agent, the positively chargeable silica fine particles are 0.1 to 2.0 mass with respect to 100 parts by mass of the toner base particles. Parts, preferably 0.3 to 1.5 parts by weight.

  In addition to the external additive particles described above, metal soap particles may be externally added to the toner base particles of the present invention. As a result, it is possible to reduce the number release rate of the externally added particles when toner particles are used, and to prevent fogging. The metal soap particles are metal salts selected from higher fatty acid zinc, magnesium, calcium, and aluminum, and examples include magnesium stearate, calcium stearate, zinc stearate, monoaluminum stearate, and trialuminum stearate. The average particle diameter of the metal soap particles is 0.5 to 20 μm, preferably 0.8 to 10 μm.

  The addition amount of the metal soap particles is 0.05 to 0.5 parts by mass, preferably 0.1 to 0.3 parts by mass with respect to 100 parts by mass of the toner base particles. When the amount is less than 0.05 parts by mass, the function as a lubricant and the function as a binder are insufficient, and when the amount is more than 0.5 parts by mass, the fog tends to increase. The addition amount of the metal soap particles is preferably 2 to 10 parts by mass with respect to 100 parts by mass of the external additive. When the amount is less than 2 parts by mass, there is no effect as a lubricant or a binder. On the other hand, when the amount exceeds 10 parts by mass, fluidity is lowered and fog is increased.

  The work function of the metal soap particles is in the range of 5.3 to 5.8, but is almost the same as the work function of the toner base particles (absolute value difference is within 0.15 eV, preferably within 0.1 eV). The work function should be

  As an external addition method, external additive particles such as large alumina particles and hydrophobic silica particles are first externally added to the toner base particles, and then the metal soap particles and positively charged silica are externally added last. It is good to be done. Further, the external additive particles having a small particle size and the alumina fine particles having a large particle size may be externally added separately to stabilize the charging characteristics when a non-magnetic one-component negatively charged spherical toner is obtained. There is no fog and the toner can suppress a decrease in transfer efficiency.

  In addition, the metal soap particles added in the post-process adhere directly to the vicinity of the external additive on the surface of the toner base particles or directly on the surface of the toner base particles. By making the work functions of the toner base particles and the metal soap particles substantially the same, In addition, the fluidity and chargeability of the toner base particles can be maintained without impairing the properties of the inorganic additive particles such as fluidity and chargeability.

  As a method for adding an external additive to the toner base particles, it is preferable to use a Henschel mixer (made by Mitsui Miike), a mechano-fusion system (made by Hosokawa Micron), a mechanomill (made by Okada Seiko), etc. When used, the first stage hydrophobic silica particles should be added at 5,000 rpm to 7,000 rpm for 1 minute to 3 minutes, and the second stage large particle size alumina fine particles or metal soap particles. In addition, it is good to set it as 1 minute-3 minutes at 5,000 rpm-7,000 rpm.

  The non-magnetic one-component negatively charged spherical toner of the present invention is measured by gel permeation chromatograph (GPC) measurement based on polystyrene in THF-soluble matter at the stage of toner mother particles or externally treated toner particles. Have a number average molecular weight (Mn) of 1,500 to 20,000, preferably 2,000 to 15,000, more preferably 3,000 to 12,000. When the number average molecular weight (Mn) is smaller than 1,500, although it is excellent in low-temperature fixability, it is inferior in colorant retention, filming resistance, offset resistance, fixed image strength, and storage stability. If it exceeds 20,000, the low-temperature fixability will be poor. The weight average molecular weight (Mw) is 3,000 to 300,000, preferably 5,000 to 50,000, and Mw / Mn is 1.5 to 20, preferably 1.8 to 8.

The flow softening temperature (Tf1 / 2) is in the range of 100 ° C to 140 ° C. When the flow softening temperature is lower than 100 ° C., the high temperature offset property is inferior. When the flow softening temperature is higher than 140 ° C., the fixing strength at a low temperature is inferior. The glass transition temperature (Tg) is in the range of 55 ° C to 70 ° C. When the glass transition temperature (Tg) is lower than 55 ° C., the storage stability is inferior. When the glass transition temperature (Tg) is higher than 70 ° C., Tf1 / 2 increases accordingly, resulting in inferior low-temperature fixability. Further, the toner of the present invention has a melt viscosity of 2 × 10 ^{3 to} 1.5 × 10 ⁴ Pa · s at a 50% outflow point, and can be suitable as an oilless fixing toner.

  The work function of the non-magnetic one-component negatively charged spherical toner of the present invention is generally 5.25 to 5.85 eV, preferably 5.35 to 5.8 eV. When the work function of the toner is less than 5.25 eV, there is a problem that the usable range of the latent image carrier and the intermediate transfer medium is narrowed. When the work function exceeds 5.85 eV, the content of the colorant in the toner is reduced. This means that the colorability is lowered, and there is a problem that the colorability is lowered.

  In addition, among the four color toners of yellow, magenta, cyan, and black, the type of binder, colorant, external additive, etc. constituting the toner particles is appropriately selected within the above-described work function range of the toner. The work functions of the obtained toner particles are adjusted so that the work functions are different from each other by at least 0.02 eV. When the four color toners are overlaid, the toner that is first developed or transferred may have a work function having the largest work function of 5.8 to 5.6 eV. The second color toner to be overlaid is 5.7 to 5.5 eV, the third color toner to be overlaid on the second color is 5.6 to 5.4 eV, and finally the third color is over. It is preferable that the fourth color toner to be overlaid with a color has a small work function range in the order of 5.5 to 5.25 eV. In particular, for the first color, it is preferable to use a toner having a work function of at least 5.6 eV.

Next, the color image forming apparatus of the present invention will be described.
FIG. 4 is a diagram for explaining the relationship among the latent image carrier, the developing unit, and the intermediate transfer medium in the color image forming apparatus of the present invention. The latent image carrier 1 is provided with a charging unit 2, an exposure unit 3, a developing unit 4 and an intermediate transfer medium 5. Although not shown in the figure, the latent image carrier may be provided with a roll brush (fur brush) as a cleaning means, and the latent image carrier is not provided with a cleaning means but is provided on an intermediate transfer medium. The carrier may be cleaner-less. In the figure, 7 is a backup roller, 8 is a toner supply roller, 9 is a toner regulating blade (toner layer thickness regulating member), 10 is a developing roller, T is a non-magnetic one-component negatively charged spherical toner, and L is a developing gap. It is.

  The latent image carrier 1 is a photosensitive drum rotating at a surface speed of 60 to 300 mm / s with a diameter of 24 to 86 mm. The surface of the latent image carrier 1 is negatively charged uniformly by the corona charger 2 and then corresponds to information to be recorded. An electrostatic latent image is formed by performing exposure 3.

  The latent image carrier may be either an organic single layer type or an organic laminated type, and the organic laminated type photoconductor is formed by sequentially laminating a charge generation layer and a charge transport layer on a conductive support via an undercoat layer. Is.

As the conductive support, a known conductive support can be used. For example, a conductive support having a volume resistance of 10 ¹⁰ Ω · cm or less, for example, 20 mm to 90 mmφ in which an aluminum alloy is processed by cutting or the like. Tubular supports, 20mm ~ 90mmφ tubular, belt-like, plate-like, sheet-like supports formed by depositing aluminum on polyethylene terephthalate film or imparting conductivity by conductive paint or molding conductive polyimide resin Examples include bodies. As another example, a metal belt in which nickel electroformed pipes, stainless steel pipes and the like are made seamless can also be suitably used.

  As the undercoat layer provided on the conductive support, a known undercoat layer can be used. For example, the undercoat layer is provided for the purpose of improving adhesion, preventing moire, improving the coatability of the upper charge generation layer, and reducing the residual potential during exposure. The resin used for the undercoat layer is preferably a resin having high resistance to dissolution with respect to the solvent used for the photosensitive layer in view of coating the photosensitive layer thereon. Soluble resins used include water-soluble resins such as polyvinyl alcohol, casein, and sodium polyacrylate, alcohol-soluble resins such as vinyl acetate, copolymerized nylon, and methoxymethylated nylon, polyurethane, melamine resin, and epoxy resin. These can be used alone or in combination of two or more. Moreover, you may make these resins contain metal oxides, such as titanium dioxide and a zinc oxide.

  As the charge generation pigment in the charge generation layer, known materials can be used. For example, phthalocyanine pigments such as metal phthalocyanine and metal-free phthalocyanine, azulenium salt pigments, squaric acid methine pigments, azo pigments having a carbazole skeleton, azo pigments having a triphenylamine skeleton, azo pigments having a diphenylamine skeleton, dibenzothiophene skeleton Azo pigments having a fluorene skeleton, azo pigments having an oxadiazole skeleton, azo pigments having a bis-stilbene skeleton, azo pigments having a distyryl oxadiazole skeleton, azo pigments having a distyrylcarbazole skeleton, perylene Pigments, anthraquinone or polycyclic quinone pigments, quinoneimine pigments, diphenylmethane and triphenylmethane pigments, benzoquinone and naphthoquinone pigments, cyanine and azomethine pigments Indigoid pigments, and bisbenzimidazole pigments. These charge generation pigments can be used alone or in combination of two or more.

  Examples of the binder resin in the charge generation layer include polyvinyl butyral resin, partially acetalized polyvinyl butyral resin, polyarylate resin, vinyl chloride-vinyl acetate copolymer, and the like. The composition ratio of the binder resin and the charge generating material is used in the range of 10 to 1000 parts by mass with respect to 100 parts of the binder resin.

  A known material can be used as the charge transport material constituting the charge transport layer, and there are an electron transport material and a hole transport material. Examples of the electron transporting material include electron accepting materials such as chloranil, tetracyanoethylene, tetracyanoquinodimethane, 2,4,7-trinitro-9-fluorenone, paradiphenoquinone derivatives, benzoquinone derivatives, and naphthoquinone derivatives. . These electron transport materials can be used alone or in combination of two or more.

  Examples of hole transport materials include oxazole compounds, oxadiazole compounds, imidazole compounds, triphenylamine compounds, pyrazoline compounds, hydrazone compounds, stilbene compounds, phenazine compounds, benzofuran compounds, butadiene compounds, benzidine compounds, and derivatives of these compounds. Can be mentioned. These electron donating substances can be used alone or in combination of two or more. The charge transport layer may contain an antioxidant, an anti-aging agent, an ultraviolet absorber and the like for preventing the deterioration of these substances.

  As the binder resin in the charge transport layer, polyester, polycarbonate, polysulfone, polyarylate, polyvinyl butyral, polymethyl methacrylate, polyvinyl chloride resin, vinyl chloride-vinyl acetate copolymer, silicone resin, etc. can be used. Polycarbonate is preferable in view of compatibility with a transport material, film strength, solubility, and stability as a coating material. The composition ratio of the binder resin and the charge transport material is used in a range of 25 to 300 parts by mass ratio with respect to 100 parts of the binder resin.

  In order to form the charge generation layer and the charge transport layer, a coating solution may be used, and the solvent varies depending on the type of the binder resin. For example, alcohols such as methanol, ethanol, isopropyl alcohol, acetone, methyl ethyl ketone, cyclohexanone, etc. Ketones, amides such as N, N-dimethylformamide, N, N-dimethylacetamide, ethers such as tetrahydrofuran, dioxane and ethylene glycol monomethyl ether, esters such as methyl acetate and ethyl acetate, chloroform, methylene chloride, Aliphatic halogenated hydrocarbons such as dichloroethylene, carbon tetrachloride, and trichloroethylene, or aromatics such as benzene, toluene, xylene, and monochlorobenzene can be used.

  The charge generating pigment may be dispersed and mixed using a mechanical method such as a sand mill, ball mill, attritor, or planetary mill.

  Coating methods for the undercoat layer, charge generation layer and charge transport layer include dip coating method, ring coating method, spray coating method, wire bar coating method, spin coating, blade coating method, roller coating method, air knife coating method, etc. Use the method. In addition, the drying after coating is preferably performed by drying at room temperature and then heating and drying at a temperature of 30 to 200 ° C. for 30 to 120 minutes. The film thickness after drying is 0.05 to 10 μm, preferably 0.1 to 3 μm, in the charge generation layer. In the charge transport layer, the thickness is in the range of 5 to 50 μm, preferably 10 to 40 μm.

  In addition, the single-layer organic photoreceptor layer has a binder and a binder, such as a charge generating agent, a charge transport agent, and a sensitizer, on the conductive support described in the above-mentioned organic laminated photoreceptor. It is prepared by coating and forming a single-layer organic photosensitive layer made of a solvent or the like. The organic negatively charged single layer type photoreceptor is preferably prepared according to, for example, Japanese Patent Application Laid-Open No. 2000-19746.

  Examples of the charge generator in the single-layer organic photosensitive layer include phthalocyanine pigments, azo pigments, quinone pigments, perylene pigments, quinothiaton pigments, indigo pigments, bisbenzimidazole pigments, and quinacridone pigments. These are phthalocyanine pigments and azo pigments. Examples of the charge transport agent include hydrazone-based, stilbene-based, phenylamine-based, arylamine-based, diphenylbutadiene-based, oxazole-based organic hole-transporting compounds, and sensitizers include various electron-withdrawing organic compounds. Examples thereof include paradiphenoquinone derivatives, naphthoquinone derivatives and chloranil which are also known as electron transport agents. Examples of the binder include thermoplastic resins such as polycarbonate resin, polyarylate resin, and polyester resin.

  The composition ratio of each component is 40 to 75% by mass of the binder, 0.5 to 20% by mass of the charge generating agent, 10 to 50% by mass of the charge transporting agent, and 0.5 to 30% by mass of the sensitizer. They are 45 to 65% by mass, charge generating agent 1 to 20% by mass, charge transporting agent 20 to 40% by mass, and sensitizer 2 to 25% by mass. The solvent is preferably a solvent that is not soluble in the undercoat layer, and examples thereof include toluene, methyl ethyl ketone, and tetrahydrofuran.

  Each component is pulverized / dispersed and mixed with a stirrer such as a homomixer, a ball mill, a sand mill, an attritor, or a paint conditioner to obtain a coating solution. The coating solution is applied onto the undercoat layer by dip coating, ring coating, spray coating or the like so as to have a film thickness of 15 to 40 μm, preferably 20 to 35 μm after drying, to form a single-layer organic photoreceptor layer.

  The developing device reversely develops the electrostatic latent image on the latent image carrying member in a non-contact manner to make a visible image. The developing device is composed of a toner containing portion that contains one-component non-magnetic toner T and does not replenish the toner, and a developing portion that consists of the developing roller 10, and the developing roller is supplied with toner by a supply roller 8 that rotates counterclockwise as shown. 10 is supplied. As shown in the figure, the developing roller rotates counterclockwise, and the toner T conveyed by the supply roller 8 is conveyed to the opposite part of the latent image carrier while being attracted to the surface of the developing roller 1. The electrostatic latent image is visualized.

The developing roller is, for example, a roller in which the surface of a metal pipe having a diameter of 16 to 24 mm is plated or blasted, or a volume resistance value of 10 ⁴ to 10 NBU, SBR, EPDM, urethane rubber, silicon rubber or the like on the central shaft peripheral surface. What formed the conductive elastic body layer of 10 < ⁸ > ohm * cm and hardness 40-70 degrees (Asker A hardness) can be used. A developing bias voltage is applied through the shaft and central axis of the pipe of the developing roller.

As the regulating blade 9, SUS, phosphor bronze, rubber plate, a thin metal plate and a rubber chip bonded to each other are used, and the work function on the toner contact surface may be 4.8 to 5.4 eV. It should be smaller than the function. The regulating blade is pressed against the developing roller by a biasing means such as a spring (not shown) or by using a repulsive force as an elastic body at a linear pressure of 0.08 to 0.6 N / cm, and the toner conveyance amount is 0. 3 to 0.6 mg / cm ² , and the toner layer thickness on the developing roller is 5 to 20 μm, preferably 6 to 10 μm. The frictional charging of the toner particles can be made sufficient. If the thickness of the toner layer on the developing roller is restricted to 2 layers or more (toner transport amount 0.7 mg / cm ² or more), spherical toner may slip through, and the triboelectric charging function cannot be made sufficient, and the small particle size The toner passes through without being in contact with the toner layer regulating member and becomes a positively charged toner, and tends to be mixed in the regulated toner layer, causing fogging and a decrease in transfer efficiency. The toner charge amount may be controlled by applying a voltage to the regulating blade 9 and injecting electric charge into the toner contacting the blade.

  The developing roller 10 is opposed to the latent image carrier 1 via the developing gap L. The development gap is preferably 100 to 350 μm. Although not shown, the DC voltage (DC) developing bias is -200 to -500 V, and the superimposed AC voltage (AC) is 1.5 to 3.5 kHz, and the PP voltage is 1000 to 1800 V. It is better to make it a condition. The peripheral speed of the developing roller that rotates counterclockwise is 1.0 to 2.5, preferably 1.2 to 2.2, relative to the latent image carrier that rotates clockwise. It is good to do.

  The toner T vibrates between the surface of the developing roller and the surface of the latent image carrier at the opposing portion of the latent image carrier and the developing roller, and the electrostatic latent image is developed. Since the holder is in contact between the surface of the developing roller and the surface of the latent image carrier while the toner 8 vibrates, even if positively charged toner is present, the negatively charged toner Enable.

  Next, the intermediate transfer medium 5 is sent between the latent image carrier 1 and the backup roller (transfer roller) 7. The transfer roller presses the intermediate transfer medium against the latent image carrier, and a voltage having a polarity opposite to that of the negatively charged toner is applied as a transfer voltage.

  Examples of the intermediate transfer medium include an electronic conductive transfer drum and a transfer belt. First, transfer belt type transfer media can be divided into types using two types of substrates. One is to provide a transfer layer as a surface layer on a resin film or a seamless belt, and the other is to provide a transfer layer as a surface layer on a base layer of an elastic body. The drum type transfer medium can also be divided into types using two kinds of substrates. One is that when an organic photosensitive layer is provided on a drum having a rigid latent image carrier, for example, an aluminum drum, the intermediate transfer medium has an elastic surface layer on a rigid drum substrate such as aluminum. A transfer layer is provided. When the support for the latent image carrier is a belt or a so-called “elastic photoreceptor” in which a photosensitive layer is provided on an elastic support such as rubber, the intermediate transfer medium is made of a rigid material such as aluminum. It is preferable that a transfer layer as a surface layer is provided on a certain drum substrate directly or via a conductive intermediate layer.

As the substrate, a known conductive or insulating substrate can be used. In the case of a transfer belt, a volume resistance of 10 ⁴ to 10 ¹² Ω · cm, preferably 10 ⁶ to 10 ¹¹ Ω · cm is preferable. It can be divided into the following two types depending on the substrate used.

  Films and seamlessly suitable materials and production methods include engineering polyimides such as modified polyimide, thermosetting polyimide, polycarbonate, ethylene tetrafluoroethylene copolymer, polyvinylidene fluoride, nylon alloy, conductive carbon black, conductive titanium oxide A semiconductive film substrate having a thickness of 50 to 500 μm in which a conductive material such as conductive tin oxide or conductive silica is dispersed is formed into a seamless substrate by extrusion molding. Further, there is a seamless belt having a fluorine coating having a thickness of 5 to 50 μm as a surface protective layer for further reducing the surface energy to prevent toner filming. As a coating method, a dip coating method, a ring coating method, a spray coating method, or other methods can be used. Note that a tape such as a PET film having a film thickness of 80 μm and a rib such as urethane rubber are attached to both ends of the transfer belt to prevent cracks, elongation and meandering at the end of the transfer belt.

  In the case of producing a substrate with a film sheet, the belt can be produced by performing ultrasonic welding on the end face to form a belt shape. Specifically, a transfer belt having desired physical properties can be produced by performing ultrasonic welding after providing a conductive layer and a surface layer on a sheet film. Specifically, when a polyethylene terephthalate film having a thickness of 60 to 150 μm is used as an insulating substrate as a substrate, aluminum or the like is vapor-deposited on the surface, and an intermediate made of a conductive material such as carbon black and a resin if necessary. A transfer layer can be obtained by coating a conductive layer and providing a semiconductive surface layer made of urethane resin, fluororesin, conductive material, and fluorine-based fine particles having higher surface resistance. When it is possible to provide a resistance layer that does not require much heat during drying after coating, it is also possible to provide the above-mentioned resistance layer after ultrasonically depositing the aluminum vapor deposited film first, and use it as a transfer belt. is there.

  The material suitable for the elastic substrate such as rubber and the production method include silicon rubber, urethane rubber, NBR (nitrile rubber), EPDM (ethylene propylene rubber), etc., and a thickness of 0.8 to 2.0 mm. After producing the semiconductive rubber belt by extrusion molding, the surface is controlled to a desired surface roughness with an abrasive such as sandpaper or polisher. The elastic layer at this time may be used as it is, but a surface protective layer can be further provided in the same manner as described above.

In the case of a transfer drum, a volume resistance of 10 ⁴ to 10 ¹² Ω · cm, preferably 10 ⁷ to 10 ¹¹ Ω · cm is preferable. The transfer drum is provided with a conductive intermediate layer of an elastic body on a metal cylinder such as aluminum as necessary to form a conductive elastic base. Further, the surface energy is lowered on the transfer drum, and a semiconductive layer is used as a surface protective layer to prevent toner filming. For example, fluorine coating having a thickness of 5 to 50 μm can be produced.

Examples of the conductive elastic substrate include silicon rubber, urethane rubber, NBR (nitrile rubber), EPDM (ethylene propylene rubber), butadiene rubber, styrene-butadiene rubber, isoprene rubber, chloroprene rubber, butyl rubber, epichlorohydrin rubber, and fluorine rubber. A conductive rubber material, such as carbon black, conductive titanium oxide, conductive tin oxide, and conductive silica, blended, kneaded, and dispersed into a rubber material such as carbon black is adhesively molded into an aluminum cylinder with a diameter of 90 to 180 mm. Then, it is preferable that the thickness after polishing is 0.8 to 6 mm and the volume resistance is 10 ⁴ to 10 ¹⁰ Ω · cm. Subsequently, a transfer drum having a desired volume resistance of 10 ⁷ to 10 ¹¹ Ω · cm is provided by providing a semiconductive surface layer made of urethane resin, fluororesin, conductive material, and fluorine-based fine particles with a film thickness of about 15 to 40 μm. be able to. The surface roughness at this time is preferably 1 μmRa or less. As another example, a transfer drum having a desired surface layer and electric resistance is formed by covering a conductive elastic substrate manufactured as described above with a semiconductive tube such as a fluororesin and shrinking by heating. It is also possible to produce it.

  A voltage of +250 to +600 V is applied as the primary transfer voltage to the conductive layer in the transfer drum or the transfer belt, and a voltage of +400 to +2800 V is used as the secondary transfer voltage in the secondary transfer to a transfer material such as paper. Is preferably applied.

The transfer roller 7 has a structure in which an elastic layer, a conductive layer, and a resistive surface layer are laminated in this order on the peripheral surface of a metal shaft having a diameter of 10 to 20 mm. The resistive surface layer can be made of a highly flexible resistive sheet in which conductive fine particles such as conductive carbon are dispersed in a resin such as a fluororesin or polyvinyl butyral, or a rubber such as polyurethane, and the surface is smooth. The volume resistance value is 10 ⁷ to 10 ¹¹ Ω · cm, preferably 10 ⁸ to 10 ¹⁰ Ω · cm, and the film thickness is 0.02 to 2 mm.

The conductive layer may be selected from a conductive resin in which conductive fine particles such as conductive carbon are dispersed in a polyester resin, a metal sheet, or a conductive adhesive, and has a volume resistance of 10 ⁵ Ω · cm or less. belongs to. The elastic layer is required to be flexibly deformed when the transfer roller is pressed against the latent image carrier, and to return to its original shape as soon as the pressure is released. It is formed using. The foamed structure may be either a continuous foamed (foamed) structure or a closed cell structure, and may have a rubber hardness (Asker C hardness) of 30 to 80, and a film thickness of 1 to 5 mm. Due to the elastic deformation of the transfer roller, the latent image carrier and the intermediate transfer medium can be brought into close contact with each other with a wide nip width. The pressing load applied to the latent image carrier by the transfer roller is 0.245 to 0.588 N / cm, preferably 0.343 to 0.49 N / cm.

  In the full-color image forming apparatus of the present invention, the transfer residual toner on the latent image carrier can be transferred to the intermediate transfer medium by making the work function of the intermediate transfer medium smaller than the work function of the toner, In addition, the amount of residual toner on the intermediate transfer medium after the transfer from the intermediate transfer medium to a recording member such as paper can be reduced.

The work function (Φ _opc ) of the surface of the latent image carrier (photoconductor) is 5.2 to 5.6 eV, preferably 5.25 to 5.5 eV, and can be used if it is less than 5.2 eV. There is a problem that it is difficult to select a charge transporting agent, and when it exceeds 5.6 eV, it is difficult to select a usable charge generating agent.

The work function (Φ _tM ) on the surface of the intermediate transfer medium is 4.9 to 5.5 eV, preferably 4.95 to 5.45 eV. If the work function (Φ _tM ) on the surface of the intermediate transfer medium is larger than 5.5 eV, it is not preferable because the material design as a toner becomes difficult, and if it is smaller than 4.9 eV, the amount of the conductive agent in the intermediate transfer medium is not preferable. There is a problem that the mechanical strength of the intermediate transfer medium is lowered due to excessive increase.

  In addition, the work function of the regulating blade is preferably made smaller than the work function of the toner, and the generation of the reversely charged toner can be further prevented.

The full-color image forming apparatus of the present invention can achieve high transfer efficiency by increasing the average circularity R of non-magnetic one-component negatively charged spherical toner particles to 0.970 to 0.985. The latent image carrier can be made cleaner-less as in the color image forming apparatus shown (when the latent image carrier is made cleaner-free, the intermediate transfer medium is provided with a cleaning means), but the work function of the spherical toner ( Φ _t ), and the relationship between the work function (Φ _OPC ) of the latent image carrier surface in the image forming apparatus and the work function (Φ _M ) of the intermediate transfer medium, Φ _t > Φ _OPC > Φ _tM The transfer efficiency can be improved, and the amount of toner remaining on the surface of the latent image carrier can be reduced.

The work function (Φ _tM ) on the surface of the intermediate transfer medium can be 4.9 to 5.5 eV, and the work function of the nonmagnetic one-component negatively charged spherical toner can be 5.25 to 5.85 eV. In the full-color image forming apparatus of the present invention, the amount of residual toner on the intermediate transfer medium after transfer to a recording member such as paper is reduced by making the work function of the intermediate transfer medium at least 0.2 eV smaller than the work function of the toner. Can be reduced.

  In the image forming apparatus shown in FIG. 4, the developing process is a full-color image forming apparatus by combining a developing device and a photoreceptor using toner (developer) of four colors consisting of yellow Y, cyan C, magenta M, and black K. FIG. 5 shows an example of the tandem system, in which no cleaning means is disposed on the latent image carrier, and the latent image carrier is cleanerless. FIG. 6A is an example of a rotary-type full-color printer according to the present invention, and a roll brush (fur brush) shown in FIG. .

  FIG. 5 is a diagram illustrating an example of a tandem color printer according to the present invention. The image forming apparatus 201 does not have a cleaning unit in the latent image carrier, and is attached to the housing 202, a paper discharge tray 203 formed on the top of the housing 202, and a front surface of the housing 202 so as to be opened and closed. In the housing 202, a control unit 205, a power supply unit 206, an exposure unit 207, an image forming unit 208, an exhaust fan 209, a transfer unit 210, and a paper feed unit 211 are disposed. In 204, a paper transport unit 212 is disposed. Each unit has a configuration that can be attached to and detached from the main body, and can be removed and repaired or replaced integrally during maintenance or the like.

  The transfer unit 210 includes a driving roller 213 disposed below the housing 202 and driven to rotate by a driving source (not shown), a driven roller 214 disposed obliquely above the driving roller 213, and the two rollers. An intermediate transfer belt 215 that is stretched between and circulated and driven in the direction of the arrow shown in the figure (counterclockwise) is provided. It is installed. As a result, the belt tension side (side pulled by the drive roller 213) 217 during driving of the intermediate transfer belt 215 is positioned below, and the belt slack side 218 is positioned above.

The drive roller 213 also serves as a backup roller for a secondary transfer roller 219 described later. A rubber layer having a thickness of about 3 mm and a volume resistivity of 1 × 10 ⁵ Ω · cm or less is formed on the peripheral surface of the driving roller 213, and the secondary transfer is performed by grounding through a metal shaft. A conductive path of the secondary transfer bias supplied via the roller 219 is used. Thus, by providing the driving roller 213 with a rubber layer having high friction and shock absorption, it is difficult for the impact when the recording material enters the secondary transfer portion to be transmitted to the intermediate transfer belt 215, thereby preventing image quality deterioration. can do.

  Further, the diameter of the driving roller 213 is made smaller than the diameter of the driven roller 214. Thereby, the recording paper after the secondary transfer can be easily peeled by the elastic force of the recording paper itself.

  Further, on the back surface of the intermediate transfer belt 215, the primary transfer member 221 is opposed to the latent image carrier 220 of single color image forming units Y, M, C, K for each color constituting the image forming unit 208 described later. And a transfer bias is applied to the primary transfer member 221.

  The image forming unit 208 is a single color image forming unit Y (for yellow), M (for magenta), C (for cyan), K (for black) that forms a plurality of (four in this embodiment) images of different colors. The monochromatic image forming units Y, M, C, and K are respectively provided with a latent image carrier 220 formed of a photosensitive member on which an organic photosensitive layer and an inorganic photosensitive layer are formed, and around the latent image carrier 220. It has a charging means 222 and a developing means 223 which are provided with a corona charger.

  The latent image carrier 220 of each monochrome image forming unit Y, M, C, K is brought into contact with the belt tension side 217 of the intermediate transfer belt 215. As a result, each monochrome image forming unit Y, M, C and K are also arranged in a direction inclined to the left in the drawing with respect to the drive roller 213. The latent image carrier 220 is driven to rotate in the direction opposite to that of the intermediate transfer belt 215 as indicated by the arrows in the figure.

  The exposure unit 207 is disposed obliquely below the image forming unit 208, and includes a polygon mirror motor 224, a polygon mirror 225, an f-θ lens 226, a reflection mirror 227, and a folding mirror 228. Are modulated and formed based on a common data clock frequency, passed through an f-θ lens 226, a reflection mirror 227, and a folding mirror 228, and then output to each monochrome image forming unit Y, M, C, K. The latent image carrier 220 is irradiated to form a latent image. Note that the optical path lengths of the monochromatic image forming units Y, M, C, and K to the latent image carrier 220 are made substantially the same by the action of the folding mirror 228.

  Next, the developing unit 223 will be described on behalf of the monochromatic image forming unit Y. In the present embodiment, since the single color image forming units Y, M, C, and K are arranged in a direction inclined to the left side in the drawing, the toner storage container 229 is arranged obliquely downward.

  That is, the developing unit 223 includes a toner storage container 229 that stores toner, a toner storage unit 230 (hatched portion in the drawing) formed in the toner storage container 229, and a toner disposed in the toner storage unit 230. The agitating member 231, a partition member 232 partitioned on the toner storage unit 230, a toner supply roller 233 disposed above the partition member 232, and abutting the toner supply roller 233 provided on the partition member 232 A charging blade 234, a developing roller 235 disposed so as to be close to the toner supply roller 233 and the latent image carrier 220, and a regulating blade 236 that contacts the developing roller 235.

  The developing roller 235 and the toner supply roller 233 are driven to rotate in the direction opposite to the rotation direction of the latent image carrier 220 as shown by the arrows in the figure, while the stirring member 231 is opposite to the rotation direction of the supply roller 233. It is rotationally driven in the direction. The toner stirred and carried by the stirring member 231 in the toner storage unit 230 is supplied to the toner supply roller 233 along the upper surface of the partition member 232, and the supplied toner is a charging blade 234 made of a flexible material. The surface of the supply roller 233 is supplied to the surface of the developing roller 235 by the mechanical adhesion force to the concavo-convex portion of the supply roller 233 and the adhesion force due to the frictional band power.

  The toner supplied to the developing roller 235 is regulated to be thinned to a predetermined thickness by the regulating blade 236. The thinned toner layer is transported to the latent image carrier 220 and develops the electrostatic latent image on the latent image carrier 220 in the development region where the developing roller 235 and the latent image carrier 220 are close to each other.

  Further, at the time of image formation, the paper feed unit 211 includes a paper feed cassette 238 in which a plurality of recording materials S are stacked and held, and a pickup roller 239 that feeds the recording materials S from the paper feed cassette 238 one by one. ing.

  The paper transport unit 212 includes a gate roller pair 240 (one roller is provided on the housing 202 side) that defines the timing of feeding the recording material S to the secondary transfer unit, a drive roller 213 and an intermediate transfer belt 215. A secondary transfer roller 219 as a secondary transfer unit that is in pressure contact with the recording medium, a main recording material conveyance path 241, a fixing unit 242, a discharge roller pair 243, and a duplex printing conveyance path 244. The toner remaining on the intermediate transfer belt 215 after the transfer to the intermediate transfer belt 215 is removed by the cleaning unit 216.

  The fixing unit 242 includes a sheet material that presses and urges at least one roller of the fixing roller pair 245 toward the other side, and a pair of rotatable fixing rollers 245 each including a heating element such as a halogen heater. The secondary image that has been secondarily transferred to the recording material S is pressed against the recording material S, and the secondary image that has been secondarily transferred to the recording material is recorded at a predetermined temperature at the nip formed by the fixing roller pair 245. Fixed to the material.

  Since the intermediate transfer belt 215 is disposed in a direction inclined to the left in the drawing with respect to the driving roller 213, a wide space is generated on the right side, and the fixing unit 242 can be disposed in the space. It is possible to realize downsizing, and heat generated by the fixing unit 242 adversely affects the exposure unit 207, the intermediate transfer belt 215, and the single-color image forming units Y, M, C, and K located on the left side. Can be prevented.

  Next, FIG. 6A is an explanatory diagram of a color image forming apparatus of a batch transfer type four-cycle rotary development system according to the present invention, which can form a full color image on both sides of a recording material such as paper. The case 10, the image carrier unit 20, the exposure unit 30 as the exposure means, the developing device (developing device) 40 as the development means, the intermediate transfer body unit 50, And a fixing unit (fixing device) 60 as fixing means. The case 10 is provided with a frame (not shown) of the apparatus main body, and each unit is attached to the frame.

  The image carrier unit 20 includes a latent image carrier (photoconductor) 21 having a photosensitive layer on the outer peripheral surface, and a charging unit (scorotron charger) 22 that uniformly charges the outer peripheral surface of the photoconductor 21. Then, the outer peripheral surface of the photoconductor 21 uniformly charged by the charging means 22 is selectively exposed with the laser light L from the exposure unit 30 to form an electrostatic latent image, and this electrostatic latent image is formed. A toner as a developer is applied to the image by a developing device 40 to form a visible image (toner image), and the toner image is primarily transferred to the intermediate transfer belt 51 of the intermediate transfer body unit 50 by the primary transfer portion T1, The secondary transfer portion T2 performs secondary transfer onto a sheet to be transferred.

  In the case 10, a conveyance path 16 that conveys a sheet on which an image is formed on one side by the secondary transfer section T <b> 2 toward a sheet discharge section (sheet discharge tray section) 15 on the top surface of the case 10, and the conveyance path 16. A return path 17 is provided for switching back the sheet conveyed toward the sheet discharge unit 15 and returning it to the secondary transfer unit T2 so as to form an image on the other side. Under the case 10, there are provided a paper feed tray 18 for laminating and holding a plurality of sheets, and a paper feed roller 19 for feeding the sheets one by one toward the secondary transfer portion T2.

  The developing device 40 is a rotary developing device, and a plurality of developing device cartridges each containing toner are detachably attached to the rotating body main body 41. In this embodiment, a yellow developer cartridge 42Y, a magenta developer cartridge 42M, a cyan developer cartridge 42C, and a black developer cartridge 42K are provided (in the drawing, yellow Only the developing device cartridge 42Y is directly depicted), and the rotating body main body 41 is rotated at a pitch of 90 degrees in the direction of the arrow, so that the developing roller 43 is selectively opposed to the photosensitive member 21 and the surface of the photosensitive member 21 Can be selectively developed.

  Further, the exposure unit 30 is configured to irradiate the photosensitive member 21 with the laser light L from an exposure window 31 made of plate glass or the like.

  As shown in FIGS. 6A and 6B, the cleaning unit 23 is provided downstream of the primary transfer roller 56 so as to face the latent image carrier 21, and a metal spring or the like is provided in the cleaner case 24, for example. A spiral rotating body 25 made of a spiral member is provided. The cleaning means 23 is attached to the cleaner case 24 and is held by a contact / separation means 26 arranged so as to be able to contact / separate during development. Further, the cleaner case 24 is provided with a lower seal 27 and an upper seal 28 to prevent the toner from dropping from the latent image carrier 21.

  After development, the toner remaining on the latent image carrier 21 is scraped off by a roll brush 29 that rotates in a reverse direction to the latent image carrier 21 and is stored in the cleaner case 24. It is conveyed in the rear direction and is transferred from the cleaner case 24 to a waste toner tank (not shown). However, it is difficult to completely remove the toner in the cleaner case 24. If the apparatus is vibrated vigorously by conveyance or the like in a state where these waste toners remain, the toner remaining inside the cleaner rises, and the apparatus Will be scattered inside. Therefore, it is preferable to provide a cleaning hole in the cleaner case 24 and suck the residual toner through the hole.

  The roll brush used in the cleaning device can be produced by the method described in JP-A-10-293439. A ribbon-shaped brush body in which a number of conductive brush bristles are pile-woven on a metal core rod roll and wound on a base fabric is wound spirally around the core rod roll, and the direction of pile weaving is perpendicular to the longitudinal direction of the brush body. Direction.

The conductive brush bristles are formed from conductive yarn in which a conductive material such as carbon black based on nylon, rayon, vinylon, polyester, acrylic, etc. is dispersed, and the resistance can be arbitrarily adjusted by the amount of the conductive carbon material. . The thickness of this conductive fiber is 600 D / F, the weave density is 100,000 F / inch ² , and the bail length is 6.5 mm. The base fabric is composed of warp yarns and weft yarns, and is composed of 40/2 thick polyester synthetic yarns. The base fabric is made of a pile weave with a wide weave of W weave and conductive direction in the longitudinal direction. A base fabric is obtained.

  After pile weaving the base fabric, back coating is performed using conductive styrene butadiene rubber (SBR) on the back surface of the base fabric. Thereafter, the base fabric is cut into 15 mm slits to form a ribbon-like brush body. The core rod roll has a shaft diameter of 6 mm, and the material of the core rod roll is KANIGEN plating. A double-sided adhesive tape is wound around the core roll. Then, a ribbon-like brush body is spirally wound on the double-sided adhesive tape. After that, when the brush roll was processed with straight hair, the outer diameter thereof was set to 15 mm to obtain a finished product of a roll brush, that is, a fur brush.

  For the produced roll brush, various synthetic fibers (manufactured by Toei Sangyo Co., Ltd.) were selected as the conductive fibers, and the work function was measured. 0.95 eV, polyester-based 4KC was 5.70 eV. In the present invention, a USV material roll brush 1 having a work function of 4.95 eV and a 4KC material roll brush 2 having a work function of 5.70 eV were used.

  The intermediate transfer body unit 50 stabilizes the state of the belt 51 at a unit frame (not shown), a driving roller 54, a driven roller 55, a primary transfer roller 56, and a primary transfer portion T1 that are rotatably supported by the frame. A guide roller 57, a tension roller 58, and the intermediate transfer belt 51 stretched around these rollers are provided, and the belt 51 is circulated and driven in the direction of the arrow in the figure.

  The primary transfer portion T1 is formed between the photosensitive member 21 and the primary transfer roller 56, and the secondary transfer portion T2 is in a pressure contact portion between the driving roller 54 and the secondary transfer roller 10b provided on the main body side. It is formed.

  The secondary transfer roller 10b can be brought into contact with and separated from the drive roller 54 (and therefore with respect to the intermediate transfer belt 51), and when it comes into contact, a secondary transfer portion T2 is formed.

  Therefore, when forming a color image, a toner image of a plurality of colors is superimposed on the intermediate transfer belt 51 with the secondary transfer roller 10b being separated from the intermediate transfer belt 51, and then a color image is formed. The secondary transfer roller 10b comes into contact with the intermediate transfer belt 51, and the paper is supplied to the contact portion (secondary transfer portion T2), whereby a color image (toner image) is transferred onto the paper. .

  The sheet on which the toner image has been transferred passes through the heating roller pair 61 of the fixing unit 60 to melt and fix the toner image, and is discharged toward the paper discharge tray unit 15. The fixing device 60 is constituted by an oilless fixing device that does not apply oil to the heating roller 61.

  Hereinafter, the present invention will be described in more detail with reference to examples.

Example 1
0.5 parts by mass of the alumina fine particles shown in Table 3 were mixed and stirred for 1 minute using a blender (manufactured by WARING) with respect to 100 parts by mass of the cyan toner base particles produced in Production Example 1 of the toner base particles described above. . Thereafter, using a flow type particle image analyzer (FPIA2100 manufactured by Sysmex), the cumulative percentage with a particle size range of 3.00 μm or less was measured on a number basis. Each result is shown in Table 4.

  Conventionally, if there are many free external additives from toner base particles, the powder characteristics and charging characteristics are affected. Especially, when continuous printing is performed, the behavior of the toner changes discontinuously. Color reproducibility, etc.) is not uniform and is said to be disadvantageous in color images.

  As is clear from the results in Table 4, it can be seen that when the work function difference between the toner base particles and the alumina fine particles is small, the toner particles are more likely to be released from the surface of the cyan toner base particles, and as the work function difference is large, the release is more difficult. It can be seen that when the work function difference between the toner base particles and the alumina fine particles is 0.4 eV or more, the α-type alumina fine particles are hardly liberated.

(Example 2)
Α-type alumina 2 (average particle size 0.23 μm) and α-type alumina 4 (average particle size 0.10 μm) shown in Table 3 with respect to 100 parts by mass of the yellow toner base particles prepared in Production Example 3 of the toner base particles described above. 0.5 parts by mass of each were mixed and stirred for 1 minute using a blender (manufactured by WARING). Thereafter, using a flow type particle image analyzer (FPIA2100 manufactured by Sysmex), the cumulative percentage with a particle size range of 3.00 μm or less was measured on a number basis. The results are shown in Table 5.

  It can be seen that the same result as in Example 1 is obtained even with the yellow toner base particles.

(Example 3)
An example of manufacturing each member in the color image forming apparatus shown in FIGS.

Preparation of organophotoreceptor A conductive support of an aluminum tube having a diameter of 30 mm, 6 parts by mass of alcohol-soluble nylon {"CM8000" manufactured by Toray Industries, Inc.} as an undercoat layer, and 4 parts by mass of titanium oxide fine particles treated with aminosilane A coating solution prepared by dissolving and dispersing in 100 parts by mass of methanol was applied by a ring coating method and dried at a temperature of 100 ° C. for 40 minutes to form an undercoat layer having a thickness of 1.5 to 2 μm.

  On this undercoat layer, 1 part by mass of an oxytitanyl phthalocyanine pigment as a charge generating pigment, 1 part by mass of butyral resin {BX-1, manufactured by Sekisui Chemical Co., Ltd.) and 100 parts by mass of dichloroethane are mixed with glass beads having a diameter of 1 mm. The pigment dispersion obtained by dispersing for 8 hours with the used sand mill was applied by a ring coating method and dried at 80 ° C. for 20 minutes to form a charge generation layer having a thickness of 0.3 μm.

  On this charge generation layer, 40 parts by mass of a charge transport material of a styryl compound of the following structural formula (1) and 60 parts by mass of a polycarbonate resin (Panlite TS, manufactured by Teijin Chemicals Ltd.) are dissolved in 400 parts by mass of toluene. The charge transport layer was formed by applying and drying by a dip coating method so that the dry film thickness was 22 μm, and an organic photoreceptor consisting of two layers was produced.

  Structural formula (1)

  A part of the obtained organic photoreceptor was cut out, and a work piece was measured as a sample piece using a surface analyzer (AC-2 type, manufactured by Riken Keiki Co., Ltd.) at an irradiation light amount of 500 nW, 5.47 eV. showed that.

Example of developing roller The surface of an aluminum pipe having a diameter of 18 mm was subjected to nickel plating (thickness 10 μm). The surface roughness (Rz) was 4 μm. The work function on the surface of the developing roller was measured under the same conditions as 4.58 eV.

Production Example of Regulating Blade A conductive urethane rubber chip having a thickness of 1.5 mm was attached to a SUS plate having a thickness of 80 μm with a conductive adhesive. The work function of the urethane rubber surface under the same conditions was 5 eV.

Preparation Example of Intermediate Transfer Belt 1 85 parts by mass of polybutylene terephthalate, 15 parts by mass of polycarbonate, and 15 parts by mass of acetylene black were premixed by a mixer in a nitrogen atmosphere, and the resulting mixture was continuously twin-screw extruder in a nitrogen gas atmosphere. Were kneaded and pelletized. The pellets were extruded into a tubular film having an outer diameter of 170 mm and a thickness of 160 μm at 260 ° C. by a single screw extruder having an annular die. Next, an inner diameter of the extruded molten tube was regulated by a cooling inside mandrel supported on the same axis as the annular die, and the tube was cooled and solidified to produce a seamless tube. A seamless belt having an outer diameter of 172 mm, a width of 342 mm, and a thickness of 150 μm was obtained by cutting into specified dimensions. The volume resistance of this transfer belt was 3.2 × 10 ⁸ Ω · cm. When the work function was measured under the same conditions, it was 5.19 eV and a normalized photoelectron yield of 10.88.

(Production of toner particles)
100 parts by mass of each of the toner base particles obtained in Production Examples 1 to 4 of the toner base particles are weighed, and the hydrophobic silica 0 having an average particle diameter of about 12 nm, which is a fluidity improver, is added to each toner base particle. 0.5% by mass of hydrophobic silica having an average particle size of about 40 nm, 0.5% by mass of hydrophobic titanium oxide having an average particle size of 20 nm, and 0.3% by mass of α-type alumina 1 in Table 3 Was added externally at 10,000 rpm for 1 minute using a laboratory mixer, then 0.3% by mass of hydrophobic positively-charged silica having an average particle size of about 30 nm and the following Table 6 according to the color of each toner base particle. Then, 0.1 wt% of the metal soap particles shown in FIG. 6 was added, and external addition treatment was performed at 10,000 rpm for 1 minute to prepare evaluation toners.

  Further, evaluation toners were prepared in the same manner as described above except that the α-type alumina 3 shown in Table 3 was used instead of the α-type alumina 1.

  The developing unit containing the evaluation toner prepared above was set in a tandem color image forming apparatus of a latent image carrier cleanerless system by the non-magnetic one-component non-contact developing system shown in FIG. The order of setting was the order of cyan developer, magenta developer, yellow developer, and black developer as viewed from the downstream side where the paper was supplied.

  Table 7 below shows the charge characteristics of the toner on the developing roller at the initial stage and after printing 20,000 character originals corresponding to 5% color originals for each color. Charge amount distribution measuring device {E-SPART Analyzer 3 The average charge amount (−μc / g) of each toner and the number of toners% measured with a mold, manufactured by Hosokawa Micron Corporation) are shown.

According to the results of Table 7, in each color toner of the present invention using α-type alumina 1, the work function (Φ _t ) of the toner base particles and the work function (Φ _A ) of the α-type alumina fine particles are used in any toner. The difference is 0.4 eV or more, and the increase in the amount of + toner after continuous printing can be suppressed. On the other hand, in the comparative color toners using the α-type alumina 3 of the comparative example, the work of the toner base particles It can be seen that the function (Φ _t ) is small in the work function (Φ _A ) of the α-type alumina fine particles and the decrease in the average charge amount is small, but there is a tendency for the amount of + toner having a reverse polarity to increase.

  Also, in Table 8 below, the standard image data N-2A “cafeteria” image conforming to JIS X 9201-1995 is output after printing 20,000 sheets of initial and 5% originals, and the first sheet and 20,001. The color reproducibility of the first sheet was evaluated and the results were shown. For color reproducibility, the quality of the first image was set to a maximum of 10 points, and the 20,001th image was subjectively evaluated.

  According to Table 8, when the output image of “cafeteria” is observed, in the present invention, the overall saturation is small and the color image quality withstands the use in comparison with the first sheet and the 20,001th sheet. On the other hand, in the comparison, the overall saturation was lowered and a dull image was given.

Example 4
For each of the toner base particles obtained in Production Examples 5 to 8 of the toner base particles, α-type alumina 1 is used for cyan toner base particles 5 and α-type is used for the other three color toner base particles. Each color toner of the present invention was produced in the same manner as in Example 3 except that alumina 2 was used and the combination of metal soaps added to the toner base particles was as shown in Table 9 below.

  Further, instead of α-type alumina 1 and 2, toners for comparison were prepared in the same manner except that α-type alumina 3 was added in the same manner at 0.3% by mass.

  The developed developing unit containing each toner was set in a four-cycle rotary type full color printer having a latent image carrier having brush cleaning means by a non-magnetic one-component non-contact developing method shown in FIG. The order of setting was such that the toner base particles were developed and transferred from toner having a large work function. That is, the order is cyan, magenta, yellow, and black. Adjustments were made so that image processing could also be performed in that order.

  The evaluation method was to measure the total cleaning amount of the latent image carrier and the intermediate transfer belt after printing 20,000 character originals corresponding to 5% color originals for each color. In addition, the standard image data N-2A “cafeteria” image conforming to JIS X 9201-1995 is output after printing 20,000 sheets of initial and 5% originals, and color reproduction of the first and 20,001 sheets. The sex was evaluated and the results were shown. The results are shown in Table 10 together with the total cleaning amount. For color reproducibility, the quality of the first image was set to a maximum of 10 points, and the 20,001th image was subjectively evaluated.

  As is apparent from Table 10, when the “cafeteria” image is observed with the comparative toner, the comparison between the first sheet and the 20,001th sheet, compared with the case where each color toner of the present invention is used. The overall saturation was lowered, giving a dull image. On the other hand, when each color toner of the present invention was used, the color image quality was not deteriorated. Further, the total cleaning amount was about 1/3 of the comparative toner, and it was determined that the charging characteristics and powder characteristics of the toner were more stable than the comparative toner.

FIG. 1 is a diagram showing a measurement cell used for measuring the work function of toner, wherein (a) is a front view and (b) is a side view. 2A and 2B are diagrams for explaining a method for measuring a work function of a cylindrical image forming apparatus member. FIG. 2A is a perspective view showing a shape of a measurement sample piece, and FIG. 2B is a view showing a measurement state. . FIG. 3 is an example of a chart in which the work function of the toner is measured using a surface analyzer. FIG. 4 is an explanatory diagram of a non-contact developing method in the image forming apparatus of the present invention. FIG. 5 shows an example of a tandem development type full-color image forming apparatus according to the present invention, and is an explanatory diagram in the case of a latent image carrier cleanerless. FIG. 6A shows an example of a four-cycle full-color printer in the image forming apparatus of the present invention, and FIG. 6B is an explanatory diagram of a cleaning unit provided in the latent image carrier.

Explanation of symbols

  1 is a latent image carrier, 2 is a charging unit, 3 is an exposing unit, 4 is a developing unit, 5 is an intermediate transfer medium, 7 is a backup roller, 8 is a toner supply roller, 9 is a toner regulating blade (toner layer thickness regulating member) ) 10 is a developing roller, T is a one-component non-magnetic toner, and L is a developing gap.

Claims (10)

It has at least a binder resin and a colorant, has a particle size distribution in which the average particle diameter based on the number is 4.5 to 9 μm, the integrated value of the average particle diameter of 3 μm or less is 1% or less, and the average In a non-magnetic one-component negatively charged spherical toner in which alumina fine particles having an average particle diameter of 0.1 μm to 1.0 μm are externally added to toner mother particles having a circularity of 0.95 to 0.99, _A non-magnetic one-component negatively charged spherical toner characterized in that the work function (Φ _t ) is at least 0.4 eV greater than the work function (Φ _A ) of the alumina fine particles. The work function (Φ _t ) of the toner base particles is 5.2 to 5.8 eV, and the work function (Φ _A ) of the alumina fine particles is 4.8 to 5.3 eV. Non-magnetic one-component negatively charged spherical toner. 2. The nonmagnetic one-component negatively charged spherical toner according to claim 1, wherein the alumina fine particles are α-type alumina fine particles. 2. The nonmagnetic one-component negatively charged spherical toner according to claim 1, wherein the toner base particles are obtained by a dissolution suspension method. 2. The non-magnetic one-component negatively charged spherical toner according to claim 1, wherein the toner base particles are those in which a colorant contained in the toner base particles is present on the surface of the toner base particles. The non-magnetic one-component negatively charged spherical toner according to claim 1, which is a full-color toner. An electrostatic latent image is formed on the latent image carrier, and the electrostatic latent image is sequentially developed by a non-magnetic one-component method using a plurality of developing units to form a color toner image, and then the latent image In a color image forming apparatus in which a toner image formed on a carrier is transferred to an intermediate transfer medium to form a color toner image, which is transferred onto a recording material and fixed, the toner includes at least a binder resin and a colorant The number-based average particle size is 4.5 to 9 μm, the integrated value of the average particle size of 3 μm or less is 1% or less, and the average circularity is 0.95 to A non-magnetic one-component negatively charged spherical toner obtained by externally adding alumina fine particles having an average particle size of 0.1 μm to 1.0 μm to toner mother particles having a particle size of 0.99, and a work function (Φ _t ) was greater than 0.4eV than the work function ([Phi _a) of the alumina particles Color image forming apparatus according to claim and. 8. A color image forming apparatus according to claim 7, wherein the developing system is a non-contact developing system. 8. The color image forming apparatus according to claim 7, wherein the color image forming apparatus employs a four-cycle rotary development system. 8. The color image forming apparatus according to claim 7, wherein the color image forming apparatus employs a tandem developing system.

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